Non-telecentric emissive micro-pixel array light modulators and methods for making the same

ABSTRACT

Emissive micro-pixel spatial light modulators with non-telecentric emission are introduced. The individual light emission from each multi-color micro-scale emissive pixel is directionally modulated in a unique direction to enable application-specific non-telecentric emission pattern from the micro-pixel array of the emissive spatial light modulator. Design methods for directionally modulating the light emission of the individual micro-pixels using micro-pixel level optics are described. Monolithic wafer level optics methods for fabricating the micro-pixel level optics are also described. An emissive multi-color micro-pixel spatial light modulator with non-telecentric emission is used to exemplify the methods and possible applications of the present invention: ultra-compact image projector, minimal cross-talk 3D light field display, multi-view 2D display, and directionally modulated waveguide optics for see-through near-eye displays.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application and claims the benefit ofU.S. Non-Provisional patent application Ser. No. 15/391,583, filed Dec.27, 2016, now allowed, which in turn claims the benefit of U.S.Provisional Patent Application No. 62/271,637, filed Dec. 28, 2015, theentirety of each of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

Non-telecentric emission spatial light modulators, emissive micro-pixeldisplays, ultra-compact image projectors, directional light modulators,multi-view 2D displays, 3D displays, near-eye displays, head-updisplays.

2. Prior Art

Spatial light modulators (SLMs) are a class of optoelectronic deviceshaving a planar array of micro-scale pixels that are typically used asan image source in display systems. Such light modulators typically fallin one of three distinctive categories: reflective, transmissive oremissive. Examples of reflective SLMs include micro mirror array devicesand liquid crystal on silicon (LCoS) devices. Examples of transmissiveSLMs include high temperature poly-silicon liquid crystal (HTPS)devices. Examples of emissive SLMs include emissive micro-pixel arraydevices. One example of an emissive micro-pixel array device may bebased on the Quantum Photonic Imager or QPI® imager described in U.S.Pat. Nos. 7,623,560, 7,767,479, 7,829,902, 8,049,231, 8,243,770 and8,567,960 and organic light emitting diode (OLED) micro-pixel arraydevices. Both reflective and transmissive SLMs typically require anexternal light source to modulate images while an emissive SLM generatesits own light. In general, all current categories of SLMs modulatetelecentric light; meaning the modulated light bundles have their chiefrays perpendicular to the plane of the light modulator pixel array. Inthe case of reflective and transmissive SLMs, telecentric lightmodulation is dictated by the design limitations of their external lightsource. Telecentric light emission is the only option available foremissive SLMs with a Lambertian emission profile such as OLED basedSLMs.

Example micro-emissive solid state light-emitting display elementssuitable for use with the embodiments herein include, withoutlimitation, those described in U.S. Pat. Nos. 7,623,560, 7,767,479,7,829,902, 8,049,231, 8,243,770 and 8,567,960. These SSL imagers featurehigh brightness, in a multi-color emissive micro-pixel spatial arraywith all of its needed drive circuitry in a single device. Within thecontext of this disclosure the term “SSL imager” is henceforth intendedto mean an optoelectronics device that comprises an array of emissivemicro-scale solid state light (SSL) emitting pixels. The SSL lightemitting pixels of such an imager, hereinafter referred to as simply SSLimagers, are typically either a light emitting diode (LED) or laserdiode (LD) whose on-off state is controlled by the drive circuitrycontained within a CMOS device upon which the emissive micro-scale pixelarray is formed or bonded. The pixels within the emissive micro-scalepixel array of an SSL imager are individually addressable through itsdrive circuitry, such as CMOS or the comparable, enabling an SSL imagerto emit light that is modulated spatially, chromatically and temporally.The multiple colors emitted by an SSL imager share the same pixeloptical aperture. In an SSL imager best suited for use with theembodiments herein, each SSL imager pixel emits at least partiallycollimated (or non-Lambertian) light, in the case of a QPI SSL imager,with an angle of divergence ranging, by design, from ±5° to ±45°. Thesize of the pixels comprising the emissive array of an SSL imager wouldtypically be in the range of approximately 5-20 microns with the typicalemissive surface area of the device being in the range of approximately15-150 square millimeter. An SSL imager preferably can be designed withminimal gap between its emissive pixel array area and the devicephysical edge, allowing a multiplicity of SSL imagers, including QPIimagers, to be tiled to create any arbitrary size emissive display area.

Although all current categories of SLMs preferably modulate telecentriclight, there is much to be gained from a non-telecentric light emissionSLM. Since reflective and transmissive SLM's non-telecentric lightmodulation capability is limited by their external light source, and anemissive OLED-based SLM cannot achieve non-telecentric light emission byvirtue of its Lambertian light emission profile, the SSL imager with itsemissive multi-color micro-pixels that emits collimated (ornon-Lambertian) light is uniquely qualified to achieve non-telecentriclight modulation. It is therefore an objective of this invention toextend the design and manufacturing methods of an SSL imager to includethe capability of non-telecentric light emission for the numerouspossible applications that stand to benefit from such capability, somefew of which are described herein by way of non-limiting examples only.

FIG. 1A illustrates the prior art design concept of a projection displaythat uses a telecentric light emission SLM. As illustrated in FIG. 1A,the divergence pattern of the light bundles 105 emitted from thetelecentric emission SLM 110 dictates the use of a large diameterprojection optics 115 which typically dictates the large optical tracklength 120, which in turn makes the overall design of a projectionsystem that uses the telecentric emission SLM 110 overly bulky. It istherefore one of the objectives of this invention to introducenon-telecentric emission SLM methods that enable smaller diameterprojection optics, and consequently achieve shorter optical tracklengths and a substantially more compact overall projection system.

FIG. 1B illustrates the prior art designs of a 3D light field displaythat uses a telecentric light emission SLM, for example U.S. Pat. Nos.8,928,969, 8,854,724 and 9,195,053. In these types of displays, an arrayof lenses (130-132) are used whereby each of these lenses (130 forexample) directionally modulates the light emitted from the sub-array ofthe SLM micro pixels 115 to subtend into a unique set of directionsdepending on the spatial position of each pixel within the sub-array ofpixels. As illustrated in FIG. 1B, the divergence pattern of thetelecentric light bundles 135 emitted from the pixels at the boundariesof each lens (130 for example) corresponding pixel sub-array wouldpartially illuminate the adjacent lenses (131 and 132 for example). Thiseffect, which is often referred to as “cross-talk”, causes undesirable“ghost” distortions in the directionally modulated 3D image. It istherefore another objective of this invention to introducenon-telecentric emission SLM methods that enable a 3D light fielddisplay exhibiting minimal cross-talk image distortion.

In the design of 3D displays, directional modulation of the emittedlight is necessary to create the 3D viewing perception. In a typical 3Ddisplay, a backlight with uniform illumination in multiple illuminationdirections is required to display images of the same scene fromdifferent directions by utilizing some combination of spatialmultiplexing and temporal multiplexing in the SLM. In these 3D displays,the light that typically comes from the directional backlight is usuallyprocessed by a directionally selective filter (such as diffractive plateor a holographic optical plate for example FIG. 1D, U.S. Pat. No.7,952,809) before it reaches the spatial light modulator pixels thatmodulate the light color and intensity while keeping its directionality.

Currently, prior art directional light modulators are a combination ofan illumination unit comprising multiple light sources and a directionalmodulation unit that directs the light emitted by the light sources to adesignated direction (see FIGS. 1D, 1E & 1F). As illustrated in FIGS.1A, 1B & 1C which depict several variants of the prior art, anillumination unit is usually combined with an electro-mechanicalmovement device such as scanning mirrors, a rotating barriers (see U.S.Pat. Nos. 6,151,167, 6,433,907, 6,795,221, 6,803,561, 6,924,476,6,937,221, 7,061,450, 7,071,594, 7,190,329, 7,193,758, 7,209,271,7,232,071, 7,482,730, 7,486,255, 7,580,007, 7,724,210, 7,791,810 andU.S. Patent Application Publication Nos. 2010/0026960 and 2010/0245957,or electro-optically such as liquid lenses or polarization switching(see U.S. Pat. Nos. 5,986,811, 6,999,238, 7,106,519, 7,215,475,7,369,321, 7,619,807, 7,952,809 and FIGS. 1A, 1B & 1C).

In addition to being slow, bulky and optically lossy, the prior artdirectional backlight units typically need to have narrow spectralbandwidth, high collimation and individual controllability for beingcombined with a directionally selective filter for 3D display purposes.Achieving narrow spectral bandwidth and high collimation requires devicelevel innovations and optical light conditioning, increasing the costand the volumetric aspects of the overall display system. Achievingindividual controllability requires additional circuitry and multiplelight sources, increasing the system complexity, bulk and cost. It istherefore an objective of this invention to introduce directional lightmodulators that overcome the limitation of the prior art, thus making itfeasible to create distortion free 3D and multi-view 2D displays thatprovide the volumetric advantages plus a viewing experience over a wideviewing angle.

Additional objectives and advantages of this invention will becomeapparent from the following detailed description of preferredembodiments thereof that proceeds with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example, and not by way oflimitation, in the Figs. of the accompanying drawings in which likereference numerals refer to similar elements.

FIG. 1A illustrates prior art light projection that uses a telecentricspatial light modulator.

FIG. 1B illustrates a prior art directional light modulator that uses atelecentric spatial light modulator.

FIG. 1C illustrates a prior art directional light modulator that uses aliquid lens.

FIG. 1D illustrates a prior art directional light modulator that usesscanning mirrors.

FIG. 1E illustrates a prior art directionally modulated backlight.

FIG. 1F illustrates a prior art directional display using adirectionally modulated backlight.

FIG. 2A illustrates a cross sectional view of a generalizednon-telecentric emissive micro pixel light modulator (SSL imager) inaccordance with this invention.

FIGS. 2B-1 AND 2B-2 illustrate top views of the light coupling topsideof the photonic layer of the non-telecentric emissive micro pixel lightmodulator of this invention.

FIGS. 2C-1 AND 2C-2 illustrate the directional light modulation aspectsof the non-telecentric emissive micro pixel directional light modulatorof this invention.

FIGS. 2D-1, 2D-2 AND 2D-3 illustrate the geometrical aspects of thedirectional light modulation pixel groups of the non-telecentricemissive micro pixel directional light modulator of this invention.

FIG. 3A illustrates a schematic cross section of an embodiment of thisinvention in which the array pixel level micro optical elements arerealized as de-centered refractive optical elements (ROE).

FIG. 3B illustrates a face view of the directional modulation layer ofan embodiment of this invention in which the array pixel level microoptical elements are realized as de-centered refractive optical elements(ROE).

FIG. 4A illustrates a schematic cross section of an embodiment of thisinvention in which the array pixel level micro optical elements arerealized as tilted refractive optical elements (ROE).

FIG. 4B illustrates a face view of the directional modulation layer ofan embodiment of this invention in which the array pixel level microoptical elements are realized as tilted refractive optical elements(ROE).

FIG. 5A illustrates a schematic cross section of a waveguide exit of anembodiment of this invention in which the array pixel level microoptical elements are realized as spatially modulated refractive opticalelements (ROE).

FIG. 5B illustrates a top view of the waveguide exit of an embodiment ofthe invention in which the array pixel level micro optical elements arerealized as spatially modulated refractive optical elements (ROE).

FIG. 6A illustrates an embodiment of this invention in which the arraypixel level micro optical elements are realized as diffractive opticalelements (DOE).

FIG. 6B illustrates an example in which the SSL imager pixels'diffractive optical elements are realized using multiple dielectriclayers that form a blazed grating.

FIG. 6C illustrates an example of the case when multi-level gratings areused to realize the desired diffraction angle across the multiplewavelengths light emission bandwidth of the SSL imager pixels.

FIG. 7A illustrates a wafer level optics (WLO) fabrication process ofthe pixel level micro optical elements of the non-telecentric emissivemicro pixel light modulator of this invention.

FIG. 7B illustrates a lithographic mask set used in the wafer leveloptics (WLO) fabrication process of the pixel level micro opticalelements of the non-telecentric emissive micro pixel light modulator ofthis invention.

FIG. 7C illustrates a wafer level optics (WLO) fabrication process of ade-centered pixel level micro optical elements of the non-telecentricemissive micro pixel light modulator of this invention.

FIGS. 7D-7M illustrate a wafer level optics (WLO) fabrication processsequence of the pixel level micro optical elements of thenon-telecentric emissive micro pixel light modulator of this invention.

FIG. 8A illustrates a design method of an ultra compact displayprojector enabled by the non-telecentric emissive micro pixel lightmodulator of this invention.

FIG. 8B illustrates the superior optical efficiency and uniformity ofthe ultra compact display projector of FIG. 8A enabled by thenon-telecentric emissive micro pixel light modulator of this invention.

FIG. 8C illustrates the superior volumetric efficiency of the ultracompact display projector of FIG. 8A enabled by the non-telecentricemissive micro pixel light modulator of this invention.

FIG. 9 illustrates a design method of a minimum cross-talk light fieldmodulator enabled by the non-telecentric emissive micro pixel lightmodulator of this invention.

FIG. 10A illustrates a top view of a multi-view 2D display enabled bythe non-telecentric emissive micro pixel light modulator of thisinvention.

FIG. 10B illustrates a side view of a multi-view 2D display enabled bythe non-telecentric emissive micro pixel light modulator of thisinvention.

FIG. 11A illustrates a side view of a waveguide light modulator enabledby the non-telecentric emissive micro pixel light modulator of thisinvention.

FIG. 11B illustrates a top view of a waveguide light modulator enabledby the non-telecentric emissive micro pixel light modulator of thisinvention.

FIG. 11C illustrates a side view of a tapered waveguide light modulatorenabled by the non-telecentric emissive micro pixel light modulator ofthis invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

References in the following detailed description of the presentinvention to “one embodiment” or “an embodiment” means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of the phrase “in one embodiment” in various places in thisdetailed description are not necessarily all referring to the sameembodiment.

In the description to follow, references are made to the word groups,such as in a directional modulation groups of micro pixels and similarreferences. When a non-telecentric emissive micro-pixel array lightmodulator in accordance with the present invention is to display a lightfield, reference to a group of pixels or to the corresponding microoptical elements is a reference to the pixels or micro optical elementsassociated with a single hogel. When the present invention is to displayone or more two dimensional scenes at the same time, reference to agroup of pixels or to the corresponding micro optical elements is areference to all pixels of the non-telecentric emissive micro-pixelarray light modulator or to one of the groups of pixels associated witha respective two dimensional scene.

The embodiments herein combine the emissive micro pixel arraycapabilities of an SSL imager with a monolithically fabricated pixellevel micro optical element (referred to in the claims as a directionalmodulation layer) to create a non-telecentric spatial light modulatorthat performs the combined functionalities of color and brightness aswell as directional modulation of the light emitted from each of itsemissive micro pixels. Pixel level micro optical elements are a class ofwafer level optics (WLO) which, in accordance with the presentinvention, are fabricated monolithically on an SSL imager wafer fromsemiconductor dielectric materials, such silicon oxide or siliconnitride, or alternatively with a UV curable polymer using ultra violet(UV) imprint lithography. As used herein, wafer level or wafer means adevice or matrix of devices having a diameter of at least 2 inches, andmore preferably 4 inches or more. Among the primary advantages of WLOare the ability to fabricate small feature micro-scale optical elementsand the ability to precisely align multiple layers of WLO opticalelements with the optoelectronics elements of devices such as the SSLimager or a CMOS sensor, for example. The alignment precision that canbe achieved by typical WLO fabrication techniques can be much less thanone micron. The combination of the individual pixel addressability ofthe emissive micro pixel array of the SSL imager and a precisely alignedmicro pixel level optical elements, herein referred to collectively asthe “non-telecentric SSL imager”, creates the first non-telecentricemissive SLM which enables the numerous applications highlighted in theprevious discussion and detailed henceforth.

In the embodiments herein, pixels' color, brightness and directionallight modulation is achieved by the combination of the SSL imageremissive pixels and light bending achieved by their associated micropixel level optics that collectively comprise the non-telecentricemission SSL imager.

FIG. 2A illustrates a general cross sectional view of an exemplarynon-telecentric emissive micro pixel (spatial) light modulator (SSLimager) 200 that may be used with the invention. As illustrated in FIG.2A, the overall structure of the exemplary SSL imager 200 is a stack ofmultiple layers comprising the photonic micro pixels array layer 205with the control layer 225 bonded to its non-emissive backside 233 andthe directional modulation layer 245 and the cover glass layer 235(optional in some embodiments) bonded to its emissive topside 230. Thephotonic layer 205 comprises the array of emissive multi-color micropixels 210 with each micro pixel being a photonic cavity defined by itsreflective sidewalls 220 and its reflective top and back side contactsthat form the topside 230 and backside 233 of the photonic layer 205;respectively. The photonic layer 205 is a stack of multiple coloremission III/V semiconductor sub-layers 215 which, when pixelated (i.e.,formed into a micro pixel array using semiconductor lithography, etchand deposition techniques), form a multi-color stack of heterojunctiondiodes within the photonic cavity of each of the micro pixels 210comprising the micro pixel array 200. Each of the micro pixels 210 iselectrically coupled to the control layer 225 with multiple contactmetal micro vias through the backside 233 and sidewalls 220 to controlthe on-off state of each pixel color emission sub-layer 215. The controllayer 225 is a complementary metal oxide semiconductor (CMOS) comprisingmultiple digital logic sub-layers designed to convert (or process) theSSL imager digital input, coupled through the CMOS contact vias, intoelectrical signals that are coupled to each pixel to modulate theiremitted light color and brightness. Depending on the geometry of theCMOS technology process used to fabricate the control layer 225, forexample 180-nm CMOS versus 65-nm or smaller geometry CMOS, the controllayer 225 can be used to implement either merely the micro pixel drivingcircuitry or to further implement the complex digital image processingof the digital image input that would lead to generating the micropixel's electrical drive signal.

FIGS. 2B-1 and 2B-2 illustrate top views of the light coupling top side230 of the photonic layer 205 of the non-telecentric emissive micropixel light modulator (SSL imager) 200 according to embodiments herein.As illustrated in FIGS. 2B-1 and 2B-2 , the light coupling topside 230of each micro pixel 210 is comprised of a multiplicity of waveguides260, which are formed on the topside sub-layer 230 using semiconductorlithography, etch and deposition techniques. As shown in FIGS. 2B-1 and2B-2 , the waveguides 260 may be located at various positions withrespect to the light coupling top side 230 of the photonic layer 205.Depending on the waveguides 260 diameter, depth spacing pattern, and thedielectric semiconductor material used, the angle of divergence of thecollimated light emission from micro pixels 210 can be tailored withinan angle of divergence ranging from ±5° to ±45°. Referring back to FIG.2A, the at least partially collimated light emitted from each of themicro pixels 210 is coupled onto their corresponding micro pixel leveloptical elements 250 comprising the directional modulation layer 245.

FIGS. 2C-1 and 2C-2 illustrates the functional aspects of thedirectional modulation layer 245 of the non-telecentric emissive micropixel light modulator (SSL imager) 200 of the embodiments herein. Asillustrated in the multiple panels of FIGS. 2C-1 and 2C-2 , the microoptical element 250 associated with each of the micro pixels 210 may bedesigned to direct (or directionally modulate) the light coupled onto itfrom its corresponding micro pixels 210 to a unique direction relativeto its perpendicular axis. The multiple panels of FIGS. 2C-1 and 2C-2illustrate two possible examples of the directional modulation patternsthat can be realized by the directional modulation layer 245 of thenon-telecentric emissive micro pixel light modulator (SSL imager) 200 ofthe embodiments herein. The first panel of FIG. 2C-1 illustrates anexample in which the directional modulation layer 245 is designed torealize a convergent directional modulation pattern with the lightemitted from the directional modulation group 270 of micro pixels 210directionally converge systematically toward the perpendicular axis fromthe peripheral edges of the directional modulation group 270 toward itscenter. The second panel of FIG. 2C-2 illustrates an example in whichthe directional modulation layer 245 is designed to realize a divergentdirectional modulation pattern with the light emitted from thedirectional modulation group 270 of micro pixels 210 directionallydiverge systematically away from the perpendicular axis from the centerof the directional modulation group 270 toward its peripheral edges. InFIGS. 2C-1 and 2C-2 , the arrows placed at the center of each of themicro pixels 210 are meant to indicate the direction of the chief ray ofthe light bundle emitted from each of the micro pixels 210 asrepresented by the angle of each respective arrow in the (x,y) plane andthe length of each respective arrow representing or suggestive of itsangle from the perpendicular axis.

FIGS. 2D-1, 2D-2 and 2D-3 illustrate the geometrical aspects of thedirectional modulation pixel groups 270 of the non-telecentric emissivemicro pixel light modulator (SSL imager) 200 of the embodiments herein.As illustrated in the multiple panels of FIGS. 2D-1, 2D-2 and 2D-3 , thegeometrical shape of the directional modulation pixel groups 270, interms of the number of pixels representing its dimensions in the (x,y)plane of the micro pixel array, can possibly be a square (see FIG. 2D-1), rectangle (see FIG. 2D-3 ) or hexagonal (see FIG. 2D-2 ) among manypossible shapes depending on the intended application. The size, inmicro pixels, of the directional pixel group 270 can extend to includeeither a sub-region of the SSL imager micro pixel array or the entiremicro pixel array of the SSL imager. In the case when the directionalpixel group 270 extends over a sub-region of the SSL imager micro pixelarray, it could be a repeated directional modulation pattern or in somecases it could be a unique directional modulation pattern for eachdirectional modulation pixel group 270 depending on the application.

The pixel level micro optical elements 250 of the directional modulationlayer 245 would have the same planar dimensions in the (x,y) plane astheir respective emissive micro pixel 210. The pixel level micro opticalelements 250 could be realized as either a refractive optical element(ROE) or a diffractive optical element (DOE). In either of these cases,the optical design parameters of each of the pixel level micro opticalelements 250 would be selected to realize the selected directionalmodulation pattern across the modulation pixel group 270 as explainedearlier. The pixel level micro optical elements 250 would be fabricatedmonolithically on the SSL imager wafer from either semiconductordielectric materials, such silicon oxide or silicon nitride, or frompolymer using ultra violet (UV) imprint lithography. In one embodiment,the fabrication of the pixel level micro optical elements 250 would beaccomplished as a sequence of lithography, etch and deposition stepsdirectly on the topside (the light emissive side) of the SSL imagerwafer that already incorporates on its topside the photonic layer 205,which incorporates the array of micro pixels 230, and on its backsidethe CMOS control layer 225. In another embodiment of this invention, thefabrication of the pixel level micro optical elements 250 would beaccomplished as a sequence of lithography, etch and deposition steps onone side of a wafer size cover glass layer 235, then the micro opticalelements 250 side of the cover glass wafer is aligned and bondeddirectly on the top side (the light emissive side) of the SSL imagerwafer that already incorporates the photonic layer 205 and the CMOScontrol layer 225. In yet another embodiment of this invention, thefabrication of the pixel level micro optical elements 250 would beaccomplished as a sequence of lithography, etch and deposition steps onone side of the cover glass layer 235, then the micro optical elements250 side of the glass cover wafer is used as a substrate to which themultiple sub-layers constituting the photonic layer 205, upon which thearray of micro pixels 230 are formed, and the CMOS control layer 225would be bonded sequentially to fabricate the non-telecentric emissivemicro pixel light modulator (SSL imager) 200 of the embodiments herein.

In another embodiment, the fabrication of the pixel level micro opticalelements 250 would be accomplished using WLO techniques in which themicro optical elements 250 would be formed by embossing a UV curablepolycarbonate polymer on one side of the cover glass layer 235, then theformed micro optical elements 250 side of the wafer is aligned andbonded directly on the top side (the light emissive side) of the SSLimager wafer that already incorporates the photonic layer 205 and theCMOS control layer 225. In this method, the layer of pixel level microoptical elements 250 would be fabricated using a master mold of thearray of micro optical elements 250 that is first fabricated using micromachining or laser ablation techniques, then copied on a UV transparentmold that would be used to emboss the UV curable polycarbonate polymeron one side of a wafer-size cover glass 235. The embossing of the arrayof micro optical elements 250 would also incorporate the embossing ofalignment marks that would be used to align the micro optical elements250 to their respective micro pixels 230 during the bonding process withthe SSL imager wafer that already incorporates the photonic layer 205and the CMOS control layer 225. In this case, the bonding of the glasscover wafer 235 with the embossed micro optical elements 250 to the ofthe SSL imager wafer, that already incorporates the photonic layer 205and the CMOS control layer 225, would be accomplished using UV curableoptical glue that would be spread or sprayed on the bonding surface ofeither or both wafers, then the wafers are brought into alignment usingalignment marks previously incorporated onto the surface of each wafer,then the aligned wafer pair is scanned with a UV laser beam orilluminated by a UV flood light to cure the optical glue bonding layerplaced on the bonding surfaces of the two wafers.

“De-Centered” Refractive Micro Optical Element (ROE)—

FIG. 3A illustrates one instantiation of the embodiment of thisinvention in which the array pixel level micro optical elements 250 arerealized as refractive optical elements (ROE). In this embodiment thepixel level refractive micro optical elements 250 directional modulationaspects are realized using de-centered micro lenses 250-1 formed bysuccessive layers of dielectric materials 310 and 320 with differentindexes of refraction. FIGS. 3A and 3B are side and top views;respectively, of the non-telecentric emissive micro pixel lightmodulator (SSL imager) 200 of the embodiments herein when realized asde-centered refractive micro optical elements 250-1. In this embodiment,the array of pixel level micro optical elements 250-1 would befabricated monolithically at the wafer level as multiple layers ofsemiconductor dielectric materials, such silicon oxide for the low indexlayer 310 and silicon nitride for the high index layer 320, usingsemiconductor lithography, etch and deposition techniques. Asillustrated in FIG. 3A, the array pixel level micro optical elements250-1 are realized using multiple layers, the dielectric materials 310and 320 with different indexes of refraction successively (sequentially)deposited to form the refractive surfaces of the pixel level microoptical elements 250-1. The top view panel of FIG. 3B illustrates thede-centered micro lenses method when used to realize an exemplarydirectional modulation group 270 whereby the de-centeration in the (x,y)plane of the refractive micro optical elements 250-1 would beproportional to the directional modulation to be realized by each of therefractive micro optical elements 250-1. As illustrated in FIG. 3B, inorder to realize the desired directional modulation pattern across theintended directional modulation pixel group 270, the center of therefractive micro optical elements 250-1 associated with the micro pixel230 at the center of the directional modulation group 270 would bealigned with the center of its respective pixel 230 but the center ofthe refractive micro optical elements 250-1 away from the center ofdirectional modulation pixel group 270 would have their centers offsetfrom the center of their respective pixels 230 with such an offsetgradually increasing for micro optical elements 250-1 further away fromthe center of the directional modulation pixel group 270. Thede-centeration offset of the refractive micro optical elements 250-1would converge toward or diverge away from the center of the directionalmodulation pixel group 270 when the directional modulation patternconverges toward or diverges away from the center of the directionalmodulation pixel group 270, respectively. The angular separation δθbetween the directional modulation realized by the individualde-centeration of the refractive micro optical elements 250-1 would bemade proportional to the desired directional modulation of the angularextent Θ. For example, for an N×N pixels modulation group 270 having theangular extent Θ, the angular separation δθ between the directionalmodulation realized by the individual de-centeration of the refractivemicro optical elements 250-1 would be equal to Θ/N.

“Tilted” Refractive Micro Optical Element (ROE)—

FIG. 4A illustrates yet another instantiation of the embodiment of thisinvention in which the array of pixel level micro optical elements 250are realized as refractive optical elements (ROE). In this embodiment,the pixel level refractive micro optical elements 250 directionalmodulation aspects are realized using tilted micro lenses 250-2 formedby successive layers of dielectric materials 410 and 420 with differentindexes of refraction. FIGS. 4A and 4B are side and top views;respectively, of the non-telecentric emissive micro pixel lightmodulator (SSL imager) 200 of the embodiments herein when realized usingtilted refractive micro optical elements 250-2. In this embodiment, thearray of pixel level micro optical elements 250-2 would be fabricatedmonolithically at the wafer level as multiple layers of semiconductordielectric materials, such as silicon oxide for the low index layer 410and silicon nitride for the high index layer 420, using semiconductorlithography, etch and deposition techniques. As illustrated in FIG. 4Athe array pixel level micro optical elements 250-2 are realized usingmultiple layers dielectric materials 410 and 420 with different indexesof refraction successively (sequentially) deposited to form therefractive surfaces of the pixel level micro optical elements 250-2. Thetop view panel of FIG. 4A illustrates the tilted micro lenses methodwhen used to realize an exemplary directional modulation group 270whereby the tilting of optical axis of the refractive micro opticalelements 250-2 would be proportional to the directional modulation to berealized by each of the refractive micro optical elements 250-2. Asillustrated in FIG. 4A, in order to realize the desired directionalmodulation pattern across the intended directional modulation pixelgroup 270, the optical axis of the refractive micro optical elements250-2 associated with the micro pixel 230 at the center of thedirectional modulation group 270 would be aligned with the axisperpendicular to the (x,y) plane of the refractive micro opticalelements 250-2 but the optical axis of the refractive micro opticalelements 250-2 away from the center of directional modulation pixelgroup 270 would have their optical axis inclined from the axisperpendicular to the (x,y) plane with such an inclination graduallyincreasing for micro optical elements 250-2 further away from the centerof the directional modulation pixel group 270. The tilting of theoptical axis of the refractive micro optical elements 250-1 wouldconverge toward or diverge away from the axis perpendicular to the (x,y)plane when the directional modulation pattern converges toward ordiverges away from the center of the directional modulation pixel group270, respectively. The angular separation δθ between the directionalmodulation realized by the individual optical axis tilting of therefractive micro optical elements 250-2 would be made proportional tothe desired directional modulation of the angular extent Θ. For example,for an N×N pixels modulation group 270 having the angular extent Θ, theangular separation δθ between the directional modulation realized by theindividual de-centeration of the refractive micro optical elements 250-2would be equal to Θ/N.

Spatially Modulated Refractive Micro Optical Element (ROE)—

FIG. 5A illustrates yet another embodiment of this invention in whichthe array of pixel level micro optical elements 250 are realized asrefractive optical elements (ROE). In this embodiment, the pixel levelrefractive micro optical elements 250 directional modulation aspects arerealized using spatially modulated micro lenses 250-3 formed bysuccessive layers of dielectric materials 510 and 520 with differentindexes of refraction. FIGS. 5A and 5B are side view and top viewillustrations; respectively, of the non-telecentric emissive micro pixellight modulator (SSL imager) 200 of the embodiments herein when realizedusing the spatially modulated refractive micro optical elements 250-3.As illustrated in FIG. 5A and FIG. 5B, in this embodiment the centers ofthe pixel level refractive micro optical elements 250-3 are aligned withtheir respective emissive micro pixels 205 and their optical axes arealso aligned perpendicular to the (x,y) plane but in the case of thisembodiment, the directional modulation is realized by using Fourier (orfield) lens micro optical elements 250-3 combined with an emissive micropixel 205 having a single waveguide 260 that is spatially modulated, orappropriately positioned in the (x,y) plane, within the pixel's opticalaperture. In FIG. 5B, the single waveguide is illustrated by the solidcircle at the center of the pixel illustrated, with the limits of itspossible spatial modulation in the x and y directions being illustratedby the dashed circles 265. In this embodiment, the Fourier lens' aspectsof the micro optical elements 250-3 may cause its chief ray to be eitheraligned with, or inclined from, the perpendicular to the (x,y) planewhen the single waveguide 260 of its respective emissive micro pixel 205is positioned at the center or offset from its optical aperture;respectively, with the inclination of chief ray of the micro opticalelements 250-3 from the perpendicular to the (x,y) plane being in thedirection of the axis extended from the center of waveguide 260 to thecenter of the pixel's micro optical element 250-3 and with angularinclination that is proportional to the spatial offset of singlewaveguide 260 from the center of its respective emissive micro pixel205. FIG. 5B illustrates the micro pixel's single waveguide spatialoffset method of this embodiment when used to realize an exampledirectional modulation group 270 whereby the micro pixel's 230 singlewaveguide 260 spatial offset from the center of its optical aperture inthe (x,y) plane would be proportional to the directional modulation tobe realized by each of the refractive micro optical elements 250-3. Asillustrated in FIG. 5A, in order to realize the desired directionalmodulation pattern across the intended directional modulation pixelgroup 270, the micro optical elements 250-3 at the center of thedirectional modulation group 270 would have the single waveguide 260 ofits associated emissive micro pixel 205 aligned with the center of itsoptical aperture but the micro optical elements 250-3 away from thecenter of directional modulation pixel group 270 would have theirassociated emissive micro pixels 205 having their single waveguide 260spatial offset from the centers of their optical apertures graduallyincreasing for the emissive micro pixel 205 and micro optical element250-3 pairs further away from the center of the directional modulationpixel group 270. The spatial offset of single waveguide 260 of theemissive pixels 230 and their respective refractive micro opticalelements 250-3 would converge toward or diverge away from the center ofthe emissive micro pixels 205 of the directional modulation pixel group270 when the directional modulation pattern diverges away from orconverges toward the center of the directional modulation pixel group270, respectively. The angular separation δθ between the directionalmodulation realized by the individual single waveguide 260 spatialoffset associated with the refractive micro optical elements 250-3 wouldbe made proportional to the desired directional modulation the angularextent Θ. For example, for an N×N pixels modulation group 270 having theangular extent Θ, the angular separation δθ between the directionalmodulation realized the refractive micro optical elements 250-3 singlewaveguide 260 spatial offset would be equal to Θ/N.

In other applications, the spatially modulated refractive micro opticalelement (ROE) of the directional modulation layer described above neednot have the micro optical element 250-3 at the center of thedirectional modulation group or have the single waveguide 260 of itsassociated emissive micro pixel 205 aligned with the center of itsoptical aperture. Further, the directional modulation layer 245 of theembodiment of FIGS. 5A and 5B might be geometrically, but notphysically, intentionally shifted in an x,y plane relative to theemissive micro pixels 205. The result would be that all the microoptical elements 250-3 so shifted would have less truncation on one endand a greater truncation on the other end. This would create adirectional bias in the emission which would then be controllable by theintentional positioning of each single waveguide in the group, or pixelarray, creating the bias while preserving the range of directionalmodulation available by selective positioning of the single waveguides.

“Diffractive” Micro Optical Element (DOE)—

FIG. 6A illustrates an embodiment of this invention in which the arraypixel level micro optical elements 250 are realized as diffractiveoptical elements (DOE). In this embodiment the pixel level micro opticalelements 250 directional modulation aspects are realized using micrograting 250-4 formed by successive layers of either metal rails ordielectric materials with different indexes of refraction. FIGS. 6A and6B are side view and top view illustrations; respectively, of thenon-telecentric emissive micro pixel light modulator (SSL imager) 200 ofthe embodiments herein when realized using micro grating diffractiveoptical elements 250-4. In this embodiment the array of pixel levelmicro grating elements 250-4 would be fabricated monolithically at thewafer level as multiple layers of semiconductor dielectric materials,such silicon oxide for the low index layer 610 and silicon nitride forthe high index layer 620, or metal rails using semiconductorlithography, etch and deposition techniques. As illustrated in FIG. 6Athe array pixel level micro grating elements 250-4 are realized usingmultiple layers of dielectric material with different indexes ofrefraction successively (sequentially) deposited to form the diffractivesurfaces of the pixel level micro optical elements 250-4 (FIG. 6B). Thetop view of FIG. 6A illustrates the micro DOE method when used torealize an exemplary directional modulation group 270 whereby the micrograting optical element 250-4 diffraction angle (measured from thenormal axis) and axial orientation of the micro grating diffractiveoptical elements 250-4 in the (x,y) plane would be proportional to thedirectional modulation to be realized by each of the diffractive microoptical elements 250-4.

As illustrated in FIG. 6A, a convergent (or divergent depending on theselected design parameters of the diffractive optical elements 250-4)directional modulation pattern would be realized across the intendeddirectional modulation pixel group 270 by having the axial orientationof the diffractive micro optical elements 250-4 associated with each ofthe emissive micro pixels 205 be aligned with radial axis of thedirectional modulation group 270 and having their diffraction angle beproportional to their radial distance from the center of the modulationgroup 270. The angular separation δθ between the directional modulationrealized by the individual diffractive micro optical elements 250-4would be proportional to the desired directional modulation angularextent or field of view (FOV) Θ of the directional modulation pixelgroup 270. For example in the case of the illustration of FIG. 6A thatshows a modulation group 270 comprised of 8×8 of the micro pixels 205,when the directional modulation angular extent or field of view (FOV) Θequals 45 degrees, the angular separation δθ between the directionalmodulation realized by the individual diffractive micro optical elements250-4 would be 5.625 degrees.

The SSL imager 200 pixels' diffractive optical elements 250-4 can berealized using transmission grating such as blazed grating or railgrating, for example. The illustration of FIG. 6B shows an example inwhich the SSL imager 200 pixels' diffractive micro optical elements250-4 are realized using multiple dielectric layers 610 and 620 havingdifferent indexes that form a blazed grating, for example using highindex silicon nitride for layer 610 and lower index silicon oxide forlayer 620. In the illustration of FIG. 6B the slant angle and pitch ofthe blazed grating would be selected to realize the desired diffractionangle of each diffractive micro optical elements 250-4 and consequentlythe directional modulation of their associated emissive micro pixels 205of the SSL imager 200. In the example of FIG. 6B, the index of the layer610 would preferably be selected to match the index of the pixel'sphotonic layer 215, thus for example, using the higher index siliconnitride for layer 610. The index difference between the high index layer610 and the low index layer 620 of the pixels' diffractive micro opticalelements 250-4 would govern the maximum diffraction angle of the pixels'diffractive optical elements 250-4 and consequently the index differencebetween the two dielectric layers 610 and 620 would be a designparameter that would affect the total angular extent or field of view(FOV) realizable by the directional modulation groups 270 of the SSLimager 200 of this embodiment. For example although FIG. 6A shows alower index dielectric material 620 capping the high index layer 610, itwould be possible to have the high index layer 610 be the top layer ofthe SSL imager 200 pixels in order to maximize the pixel's diffractionangular extent and consequently the realizable field of view (FOV) ofthe SSL imager 200 directional modulation groups 270. In order tomaximize the index difference between the two layers 610 and 620 of thepixels' diffractive micro optical elements 250-4, it would be beneficialin this case for the top layer 620 to be an air gap. In this case, thecover glass layer 235 would be bonded on top side of the SSL imager 200with the addition of spacers that would allow a thin air gap layer 620between the high index layer 610 and the glass cover 235. In order tofurther maximize the field of view (FOV) realizable by the SSL imager200 directional modulation groups 270 of this embodiment, it would alsobe possible to etch the diffractive micro optical elements' 250-4 lowerlayer 610 surface directly into the top side 230 of the photonic layer215 of the SSL imager 200 pixels since, as explained earlier, thephotonic layer 215 is fabricated from III/V semiconductor material, suchas gallium nitride (GaN) for example, which typically has high index ofrefraction. Similar to the previous case of this embodiment, in thiscase it would also be beneficial to maximize the realizable FOV evenfurther by having the top layer 620 of the diffractive micro opticalelements 250-4 be an air gap layer. In this case also, the cover glasslayer 235 would be bonded on top side of the SSL imager 200 with theaddition of spacers that would allow a thin air gap layer between thehigh index layer 610 and the glass cover 235.

As explained earlier, the SSL imager 200 pixels can emit light withmultiple wavelengths from each pixel aperture. In the case when the SSLimager 200 pixels emit light with multiple wavelengths, the diffractiveoptical elements 250-2 would be realized using wideband transmissiongratings or multi-level gratings designed to achieve the desireddiffraction angle across the light emission bandwidth of the SSL imager200 pixels. In the case when wideband transmission gratings are used,the SSL imager 200 pixels diffractive optical elements 250-2 could berealized using a multiplicity of layers of dielectric materials withalternating high and low indexes for each such layer index. The index ofsuch layers together with the formed grating slant angle and pitch wouldbe selected to realize the desired pixel's diffractive angle within eachsub-band of the SSL imager 200 pixels' light emission bandwidth. FIG. 6Cillustrates an example of the case when multi-level gratings are used torealize the desired diffraction angle across the multiple wavelengthslight emission bandwidth of the SSL imager 200 pixels. In this examplecase, two dielectric layers 630 and 640 with differing indexes are usedto form a multi-level grating with a different grating pitch within eachlayer whereby the grating pitch of each layer being designed todominantly diffract light within a given sub-band of the SSL imager 200pixels light emission bandwidth. The pitch and index of each of the twolayers 630 and 640 would be selected through an iterative design processthat would take into account the collective diffractive action of thegrating multi-level across the entire multiple wavelength emissionbandwidth of the SSL imager 200 pixels. In the example of FIG. 6C, theindex of the layer 630 would preferably be selected to match the indexof the pixel's photonic layer 205. In addition, it would be possible tohave the high index layer 630 be the top layer of the SSL imager 200pixels in order to maximize the pixel's diffraction angular extent andconsequently the realizable field of view (FOV) of the SSL imager 200directional modulation groups 270. In this embodiment, the cover glasslayer 235 would be bonded on top side of the SSL imager 200 with theaddition of spacers that would allow a thin air gap layer between thehigh index layer 630 and the glass cover 235.

Directional Modulation Layer 245 Fabrication Method—

As explained earlier, the pixel level micro optical elements 250 of theprevious embodiments would be used to directionally modulate, collectand/or collimate the light emitted from their corresponding emissivemicro pixels 205 and as such would have optical apertures which areequal to and precisely aligned, within at least less than 10% accuracy,with their corresponding micro pixels 230 of the non-telecentricemissive micro pixel light modulator (SSL imager) 200 of this invention.The pixel level micro optical elements 250 of the previous embodimentscan be fabricated using a variety of nano-imprint lithographictechniques such as patterning using Phase, Grayscale, entire domain orsub domain masks, additive lithographic sculpting that use binary masksas well as various direct write techniques. Photo resist (heat) reflowand molding could also be employed for fabrication of the micro opticalelements 250 to increase the smoothness of the formed surfaces. AdditiveLithography using a sub domain binary mask set will be used herein as anexample to illustrate a typical method for the fabrication of exemplaryROE pixel level micro optical elements 250 of the non-telecentricemissive micro pixel light modulator (SSL imager) 200 of this invention.

Wafer Level Optics Mask Set—

The fabrication process sequence of the pixel level micro opticalelements 250 begins with the fabrication of a set of lithography subdomain masks that captures the binary shape specifications of the microoptical elements 250. The fabrication process of the sub domain masksinvolves identifying the symmetry within the specified features of thepixel level micro optical elements 250 to be fabricated and breakingdown the identified symmetry to an orthogonal or non orthogonal set ofbasis. FIG. 7A illustrates the orthogonal and non orthogonal basis setfor an exemplary rotationally symmetric pixel level refractive microoptical elements 250 generated by this process. The specified binarysurface shape of the micro optical elements 250 will be achieved laterduring the fabrication process by controlling the exposure dose of eachelement of the orthogonal or non orthogonal basis set during lithographyas illustrated in FIG. 7B.

As illustrated in FIG. 7A, the rotationally symmetric refractive microoptical elements 250 would be represented by the two dimensional basisset of orthogonal (rings) or non orthogonal (circles) elements. Forrealizing the pixel level micro optical elements 250 as a de-centeredROC of the previous embodiment, at each micro pixel 230 position, therequired de-centering shift is applied to the generated basis set andthen truncated accordingly after each of the basis is aligned with themicro pixel 230 aperture specified by the design. FIG. 7C illustratestwo example cases, one where the micro optical elements 250 axis lies atthe center of the aperture of the micro pixel 230 and a second casewhere the micro optical elements 250 axis is shifted from the center ofthe aperture of the micro pixel 230. This process is then repeatedacross the entire array of micro pixels 230 mask alignment referencecoordinates to create a multilayer mask set for the full aperture of theemissive micro pixel light modulator (SSL imager) 200 device. Equivalentorthogonal and non-orthogonal basis elements are then aligned with thearray of emissive micro pixel 230 mask alignment reference coordinatesacross the SSL imager 200 aperture to form separate mask layers. Thesemask layers can then be separated and placed on well known locations ona single reticle or on multiple reticles to be used in the wafer levelmicro optics lithography fabrication process of the micro opticalelements 250. This entire process of masking layers formation can beaccomplished using a standard mask editing software such as LEdittypically used in the creation of semiconductors lithography masks. Itshould be noted that this mask formation process would be repeated forevery optical surface comprising the pixel level micro optical elements250 to create a full mask set for the wafer level optic fabrication ofthe non-telecentric emissive micro pixel light modulator (SSL imager)200.

Although the preceding discussion outlined the process of forming thelithography mask set for the case when the pixel level micro opticalelements 250 are realized in accordance with the embodiment describedearlier as a de-centered ROE, a person skilled in the art will readilyknow how to apply the described lithography mask set formation processin the cases of other described embodiments when the micro opticalelements 250 are realized as tilted ROE or as a DOE.

Wafer Level Optics Fabrication Sequence—

FIGS. 7D-7M illustrate the fabrication process sequence of the pixellevel micro optical elements 250. After the wafer level optics mask setis formed in accordance with the preceding discussion, a substrate ofchoice is coated with a thin layer, preferably few microns, of adielectric material, herein referred to as dielectric-1 (FIG. 7D), usingsemiconductor material deposition tools such as plasma enhanced chemicalvapor deposition (PECVD). The deposited dielectric-1 layer could beamorphous but needs to be sufficiently transparent within the targetoptical spectrum, for example within the visible light 400 nm to 650 nmspectrum and specifically selected to introduce minimal stresses on thesubstrate wafer. The deposited dielectric-1 layer would typically be thelow index material surrounding other high index material layers thatwould comprise the pixel level micro optical elements 250. Alignmentmarks are then patterned onto the topside of the deposited dielectric-1layer to be used for aligning subsequent layers of the pixel level microoptical elements 250.

A photoresist appropriately chosen and characterized is then coated ontop of dielectric-1 layer and Additive Lithography is performed usingthe fabricated mask set to create a negative of that surface of thepixel level micro optical elements 250 (FIG. 7E). In the AdditiveLithography process, the negative surface would be created on thephotoresist layer by the successive alignment and exposure using thevarious masks of the set with an alignment tolerance of less than 100 nmor preferably in the range of 50 nm (FIG. 7F). The created shape of thephotoresist surface would be optimized by adjusting the exposure andfocus offset parameters for each of the lithographical steps for thevarious masks of the set as illustrated in FIG. 7B. This step isfollowed by the appropriate metrology measurements to confirm that thecreated photoresist negative surface is compliant with the surfacedesign specification (or optical prescription) of the 1^(st) surface ofthe pixel level micro optical elements 250.

Once the specification compliance of the photoresist negative surface isconfirmed, the micro optical elements 250 would be etched using theappropriate chemistry on a reactive ion etching (RIE) tool that canprovide 1:1 selectivity between the photoresist and the dielectric-1layers (FIG. 7G). Etching time needs to be adjusted based onpre-characterized etch rate in order to avoid over-etching into thedielectric-1 layer and to ensure that the shape on the photoresist isfaithfully transferred on the dielectric-1 layer with minimal defectsformed during the etching step. A metrology measure following this stepis used to confirm the dielectric-1 layer etched surface is compliantwith the surface design specification (or optical prescription) of themicro optical elements 250. After the etch and metrology steps, thewafer dielectric-1 layer surface is thoroughly cleaned to ensure removalof all polymer residues and other contaminants from the fabricatedsurface of the wafer. At the end of this step, the first surface of themicro optical elements 250 would be created on the dielectric-1 layer inaccurate alignment with the micro pixels 230 across the entire wafersurface with the created optical surface.

After the dielectric-1 layer surface is fabricated, the wafer is coatedwith a relatively thick conformal layer of a high index dielectric-2layer (FIG. 7H). The thickness of dielectric-2 layer should besufficient to accommodate the optical features of the micro opticalelements 250 while being highly transparent with minimal stress. Thedeposited surface of the dielectric-2 layer then undergoes aplanarization process using chemical mechanical polishing (CMP) tool toobtain a nearly flat surface across the wafer with minimal totalthickness variation (TTV) (FIG. 7I). The dielectric-2 layer wafersurface is then coated with photoresist then processed, in similar stepsas described for dielectric-1 layer, using Additive Lithography followedby etching to create the 2^(nd) surface of the pixel level micro opticalelements 250 on the dielectric-2 layer surface (FIG. 7J-L).

After the fabrication of the 1^(st) and 2^(nd) surfaces of the pixellevel micro optical elements 250 as shown in FIGS. 7K and 7L, a thirdlayer of dielectric material, designated as dielectric-3 layer, isdeposited on the top of the wafer surface and planarized to the requiredthickness and TTV specifications (FIG. 7M). The dielectric constant andindex of refraction of the dielectric layers dielectric-1, dielectric-2and dielectric-3 would be selected based on the optical prescription ofthe pixel level micro optical elements 250 and typically in mostapplications dielectric-1 and dielectric-3 would have the same index ofrefraction value that lower than dielectric-2 index of refraction value.

The described WLO fabrication steps would be repeated on the top ofdielectric-3 layer wafer surface if a second optical element is to beadded in accordance with the optical prescription of the pixel levelmicro optical elements 250.

After all the optical elements of the pixel level micro optical elements250 are fabricated on top of the substrate wafer, the wafer surface iscoated with a bonding intermediary layer, polished to the appropriatebonding specification then aligned bonded, using the alignment marksadded earlier in the process, to the top photonic layer 205 surface.

In one embodiment of this invention, the WLO fabrication processdescribed in the preceding paragraphs is used to fabricate the pixellevel micro optical elements 250 on the top of the cover glass wafer 235as a substrate then the fabricated wafer is used as a substrate uponwhich the pixelated photonic layers stack 205 would be bonded and formedsequentially. At the end of that fabrication sequence, the formed waferwould be aligned bonded to the topside of the CMOS control layer 225.

In another embodiment of this invention, the WLO fabrication processdescribed in the preceding paragraphs is used to fabricate the pixellevel micro optical elements 250 on top of the cover glass wafer 235 asa substrate then the fabricated wafer is aligned bonded to the photoniclayer 205 top surface of the wafer formed separately that comprises thephotonic layer stack 205 bonded sequentially to the topside of the CMOScontrol layer 225.

In yet another embodiment of this invention, the WLO fabrication processdescribed in the preceding paragraphs is used to fabricate the pixellevel micro optical elements 250 on top of the wafer formed separatelythat comprises the photonic layer stack 205 bonded sequentially to thetopside of the CMOS control layer 225, then the cover glass wafer isbonded on the top of the fabricated pixel level micro optical elements250. In the WLO fabrication process for this case, the 2^(nd) surface ofthe pixel level micro optical elements 250 will be fabricated first ontop of the pixelated photonic layers stack 205, then the 1^(st) surfaceof the pixel level micro optical elements 250 would be fabricated ontop. In still other embodiments, particularly using other fabricationprocesses described herein for the directional modulation layers andusing this fabrication process, the glass cover layer 235 would bebonded on the top side of the SSL imager 200 with the addition ofspacers that would allow a thin air gap layer 620 between the high indexlayer 610 and the glass cover 235. Each of the aforementionedembodiments would have its advantages depending on the intendedapplication.

FIGS. 7D-7M illustrate the WLO fabrication process described in thepreceding paragraphs to fabricate the pixel level micro optical elements250 on the on top of the cover glass wafer 235 as a substrate. AlthoughFIGS. 7D-7M illustrate the described the WLO fabrication process in thecase of the pixel level micro optical elements 250 being a ROEfabricated on top the glass cover wafer 235 as a substrate, thedescribed fabrication sequence equally applies in the case of thenumerous embodiments described including the case when the pixel levelmicro optical elements 250 being a DOE fabricated within the context ofany of the WLO fabrication process embodiments of the previousparagraphs.

Ultra Compact Projector—

FIG. 8A illustrates a design method of an ultra compact displayprojector enabled by the non-telecentric emissive micro pixel lightmodulator (SSL imager) 200 of the embodiments herein. In thisembodiment, the directional modulation layer 245 of the SSL imager 200is designed to realize a convergent directional modulation patterncausing the light emitted from the directional modulation group 270 ofmicro pixels 210 to directionally converge systematically toward theperpendicular axis from the peripheral edges of the directionalmodulation group 270 toward its center. In this case, the directionalmodulation group 270 extends across the entire emissive optical apertureof the SSL imager 200. As illustrated in FIG. 8A, the pixel level microoptical elements 250 would directionally modulate the light emitted fromSSL imager 200 micro pixels to achieve maximum fill factor of theoptical aperture of the first optical element L-1 of the projectionoptics 810 which in turn is designed to further redirect the light raystoward the second optical element L-2 optical aperture while maintainingthe fill factor at a maximum. Optical elements L3 and L4 are used formagnification of the projected image. The projector design of thisembodiment achieves less than an 8 mm optical track length with a3.6×6.4 mm SSL imager emissive aperture size while achieving a fairlyuniform optical efficiency. The actual projector has cross-sectionaldimensions of 5.82 mm×8.05 mm, with a height of 7.86 mm. Besides itsvolumetric efficiency, the ultra compact display projector of FIG. 8Awould enable the attainment of high optical efficiency and brightnessuniformity. As shown in FIG. 8B, the projector design of this embodimentachieves almost 83% optical efficiency with less than 15% center tocorner roll off compared to 22.8% optical efficiency for a design thatdoes not use the non-telecentric emissive micro pixel light modulator(SSL imager) 200 of the embodiments herein. With the minimal opticaltrack length it achieves, the projector design of this embodiment wasused to fabricate the ultra compact, full color projector pictured inFIG. 8C having a total volume of less than 0.3 cc. To the best of theinventors' knowledge, this is volumetrically the smallest HD projectorever designed and fabricated, which makes it ideal for mobile displayapplications such as embedded and attached mobile projectors as well asnear-eye head mounted displays (HMD).

Minimum Cross-Talk Light Field Modulator—

FIG. 9 illustrates a design method of a minimum cross-talk light fieldmodulator enabled by the non-telecentric emissive micro pixel lightmodulator (SSL imager) 200 of this invention. In this embodiment the“cross-talk” between holographic elements (hogels) and the undesirable3D image “ghost” distortions it causes would be substantially reduced oreliminated altogether by making the SSL imager 200 emissionnon-telecentric across the optical apertures of each of the hogel lenses930-932 as illustrated in FIG. 9 . That is to say in this embodiment,the directional modulation layer 245 of the SSL imager 200 would bedesigned to realize a convergent directional modulation pattern causingthe light emitted from the directional modulation group 270 of micropixels 210 to directionally converge systematically toward theperpendicular axis from the peripheral edges of the directionalmodulation group 270 toward its center. In the case of this embodiment,the directional modulation group 270 would extend across the sub-arrayof SSL imager 200 emissive micro pixels corresponding to (or associatedwith) the optical aperture of each of the hogel lenses 930-932 of FIG. 9. With the design method of this embodiment the pixel level microoptical elements 250 of the SSL imager 200 sub-array of micro pixels 210associated with each of the hogel lenses 930-932 would be designed suchthat the light emission from the sub-array of micro pixels 210 wouldremain substantially confined within the optical apertures of theirassociated hogel lenses 930-932 apertures, thus minimizing the lightleakage or cross-talk between adjacent the hogel lenses 930-932. Withthat being achieved, the light leakage between light field viewsmodulated by the SSL imager 200 would be minimized, making the viewsfrom different directions having no ghost interference from otherdirections.

In this embodiment, the light emitted from each of the SSL imager 200micro pixels 210 would be sufficiently collimated and directionallymodulated (or directed) by the pixel's micro optical elements 250 toefficiently fill in their associated hogel lens with minimal orsubstantially no light leakage into adjacent hogel lenses. Thus inaddition to minimizing the cross-talk between directionally modulatedviews, the directional light modulator of FIG. 9 enabled by thenon-telecentric emissive micro pixel light modulator (SSL imager) 200 ofthis invention would also achieve higher optical efficiency anduniformity across its field of view (FOV).

Multi-View Display—

FIG. 10A and FIG. 10B illustrate a top view and side view, respectively,of a multi-view 2D display design method enabled by the non-telecentricemissive micro pixel light modulator (SSL imager) 200 of this invention.In this embodiment, the SSL imager 200 emissive pixels 210 array andtheir associated micro optical elements 250 of the directionalmodulation layer 245 would be spatially partitioned into directionalmodulation sub-arrays or directional modulation groups 270. Asillustrated in FIG. 10B the directional modulation layer 245 of the SSLimager 200 of this embodiment may be designed to realize a divergentdirectional modulation pattern that would cause the light emitted fromthe directional modulation group 270 of micro pixels 210 todirectionally diverge systematically into a unique set of directionsaway from the perpendicular axis of the directional modulation group270. In this embodiment, the size of the directional modulation group270 in terms of the number of emissive pixels 210 will determine thenumber of views that can supported by the multi-view display. Forexample, a 64-view multi-view display can be realized using an 8×8directional modulation group 270 of FIG. 10A with each of the pixels ineach of the modulation groups across the display aperture being designedto emit light in a unique direction that is uniformly and angularlyspaced within the targeted field of view (FOV) of the multi-viewdisplay. In this embodiment, the light emitted from each of the SSLimager 200 micro pixels 210 would be sufficiently collimated anddirectionally modulated to a specific unique direction by the pixel'smicro optical elements 250.

Waveguide Light Modulator—

FIG. 11A illustrates a design method of a Waveguide Light Modulatorenabled by the non-telecentric emissive micro pixel light modulator ofthis invention. As illustrated in FIG. 11A, the Waveguide LightModulator of this embodiment would be comprised of the SSL imager 200with its directional modulation layer coupled onto the optical inputaperture 1120 of the waveguide 1110 which has the reflective opticslayer 1130 coated to one of its sides to define its optical outputaperture 1140. In this embodiment the SSL imager 200 emissive pixels 210array and their associated micro optical elements 250 of the directionalmodulation layer 245 would direct the light emitted from each of the SSLimager 200 pixels in a unique direction within the waveguide angularrange of the waveguide 1110. In the case of a total internal reflection(TIR) waveguide 1110, such as that illustrated in the FIG. 11A, thelight emitted from each of the SSL imager 200 pixels would bedirectionally modulated by the pixel's associated micro optical elements250 in a unique direction within the tangential (lateral) and vectorial(elevation) planes that will set forth the wave guiding angle of thelight emitted from that pixel as well as the lateral divergence from thepixel's (x,y) coordinates. The directional modulation of the lightemitted by the SSL imager 200 pixels in lateral plane would serve todetermine the total expansion (or magnification) of the image beingmodulated by the SSL imager 200 pixel array as the light emitted fromits pixel array propagate through the waveguide. In effect thedirectional modulation of the light emitted by the SSL imager 200 pixelsin lateral plane would serve to determine the x-axis magnificationfactor of the image being modulated by the SSL imager 200 pixel arrayand coupled into the waveguide. The directional modulation of the lightemitted by the SSL imager 200 pixels in vectorial plane would serve todetermine the angle at which the light emitted (and modulated) from eachof the SSL imager 200 pixels would propagate through the waveguide. Withthe waveguide reflective optics layer 1130 typically being designed tobreak the TIR condition for light rays being guided through thewaveguide at progressively lower angle further away from the waveguideinput optical aperture 1120 into which the SSL imager 200 is opticallycoupled, the light emitted by the SSL imager 200 pixels anddirectionally modulated by its micro optical elements 250 in vectorialplane at a progressively smaller angles within the waveguide TIR angularrange would propagate further away from waveguide input optical aperture1120 before its TIR guiding condition is broken (collapsed) by thewaveguide reflective optics layer 1130 directing the light more directlytoward the output aperture 1140 of the waveguide 1110. In effect thedirectional modulation of the light emitted by the SSL imager 200 pixelsin vectorial plane would serve to determine the y-axis magnificationfactor of the image being modulated by the SSL imager 200 pixel arrayand coupled into the waveguide. When the directional modulation of thelight emitted by the SSL imager 200 pixels in the tangential (lateral)and vectorial planes are properly selected for each of its pixels, thedirectional modulation of the light emitted by the SSL imager 200 ofthis invention would enable the magnification and relay of the image itis modulating and coupling into the waveguide input optical aperture1120 to the waveguide output optical aperture 1140. As an alternative,the output aperture may itself include transmissive optics to break theTIR condition at the output aperture 1140.

The directional modulation design method of this embodiment is furtherillustrated in FIG. 11B which shows a top view of the SSL imager 200enabled Waveguide Light Modulator of this invention. In FIG. 11B the SSLimager 200 pixels' coordinates within the waveguide input opticalaperture 1120 are designated as (x,y) coordinates while the WaveguideLight Modulator pixels' coordinates within the waveguide output opticalaperture 1140 are designated as (X, Y) coordinates. As illustrated inFIG. 11B, the SSL imager 200 pixels directional modulation angles in thelateral and vectorial planes cause the light emitted from each of theSSL imager 200 pixels and coupled into the waveguide at a given (x,y)coordinates within the waveguide input optical aperture 1120 to beuniquely mapped to given (X, Y) coordinates within the waveguide outputoptical aperture 1140. In effect the SSL imager 200 pixels' directionalmodulation method of this embodiment together with an appropriatelydesigned waveguide reflective optics layer 1130 would enable thesynthesis of a given optical transfer function that realizes bothmagnification and relay between the waveguide input and output opticalapertures 1120 and 1140; respectively. It should be added that in thisembodiment, the collimation angle of the light bundles emitted by theSSL imager 200 pixels would be selected to be outside the TIR angularrange of the waveguide 1110 for proper functioning of the outputaperture 1140 without special provisions for the emission.

Tapered Waveguide Light Modulator—

In an alternative embodiment, illustrated in FIG. 11C, the SSL imager200 based Waveguide Light Modulator may be realized using the taperedwaveguide 1150 whereby the tapering angle (or slope) of one surface ofthe waveguide 1150 is selected to break the TIR condition for light raysbeing guided through the waveguide 1150 at a progressively lower angle(closer to a line perpendicular to the local waveguide surface) furtheraway from the waveguide input optical aperture 1160 into which the SSLimager 200 is optically coupled. The tapering of one surface of thewaveguide 1150 in this embodiment performs the equivalent opticalfunction of the diffractive optics layer 1130 of the previousembodiment. In this embodiment, the SSL imager 200 emissive pixels 210array and their associated micro optical elements 250 of the directionalmodulation layer 245 would direct the light emitted from each of the SSLimager 200 pixels in a unique direction within the waveguide angularrange of the tapered waveguide 1150. As illustrated in the FIG. 11C, thelight emitted from each of the SSL imager 200 pixels would bedirectionally modulated by the pixel's associated micro optical elements250 in a unique direction within the tangential (lateral) and vectorial(elevation) planes that will set forth the wave guiding angle of thelight emitted from that pixel as well as the lateral divergence from thepixel's (x,y) coordinates. The directional modulation of the lightemitted by the SSL imager 200 pixels in the lateral plane would serve todetermine the total expansion of the image being modulated by the SSLimager 200 pixel array as the light emitted from its pixel arraypropagates through the tapered waveguide 1150. In effect, thedirectional modulation of the light emitted by the SSL imager 200 pixelsin lateral plane would serve to determine the x-axis magnificationfactor of the image being modulated by the SSL imager 200 pixel arrayand coupled into the waveguide. The directional modulation of the lightemitted by the SSL imager 200 pixels in vectorial plane would serve todetermine the angle at which the light emitted (and modulated) from eachof the SSL imager 200 pixels would propagate through the waveguide. Withthe tapered surfaces of the waveguide 1150 being designed to break theTIR condition for light rays being guided through the waveguide atprogressively lower angle (closer to a perpendicular to the localsurface of the tapered waive guide 1150) further away from the waveguideinput optical aperture 1160 into which the SSL imager 200 is opticallycoupled, the light emitted by the SSL imager 200 pixels anddirectionally modulated by its micro optical elements 250 in thevectorial plane at a progressively lower angles within the waveguide TIRangular range would propagate further away from waveguide input opticalaperture 1160 before it's TIR guiding condition is broken (collapsed) bythe tapered surface of the waveguide 1160. In effect, the directionalmodulation of the light emitted by the SSL imager 200 pixels in thevectorial plane would serve to determine the y-axis magnification factorof the image being modulated by the SSL imager 200 pixel array andcoupled into the tapered waveguide 1160. When the directional modulationof the light emitted by the SSL imager 200 pixels in the tangential(lateral) and vectorial planes are properly selected for each of itspixels, the directional modulation of the light emitted by the SSLimager 200 of the embodiments herein would enable the magnification andrelay of the image it is modulating and coupling into the taperedwaveguide 1160 input optical aperture 1120 to the waveguide outputoptical aperture 1140. In effect the SSL imager 200 pixels directionalmodulation method of this embodiment together with an appropriatelydesigned tapered waveguide 1150 would enable the synthesis of a givenoptical transfer function that realizes both magnification and relaybetween the tapered waveguide 1150 input and output optical apertures1160 and 1170; respectively. It should be added that in this embodiment,the collimation angle of the light bundles emitted the SSL imager 200pixels would be selected to be within the TIR angular range of thetapered waveguide 1150. As an alternate, certain surfaces of the taperedwaveguide such as part of the lower surface of the tapered waveguide maybe coated with a reflective coating, if desired, to allow a lastreflection when the TIR condition has already been broken.

It should be noted that the two previous embodiments of the SSL imager200 based Waveguide Light Modulator can be used to create opticalsee-through (OST) near-eye or head-mounted display (HMD). In each ofthese embodiments, as alternate embodiments, the SSL imager may insteadhave its output coupled into an input aperture at the end or edge of thewaveguide 1110 and achieve the same of similar results. Also thewaveguides themselves may have other shapes, and are not limited torectangular shapes as shown.

Thus, using the wafer level fabrication techniques for the wafer leveloptics, the entire non-telecentric emissive micro-pixel array lightmodulator may be fabricated at the wafer level and then the wafer levelassembly diced to obtain the final products.

Also, while FIG. 2C-1 illustrates an embodiment wherein the lightconverges from the center of the pixel group or the entire array, andFIG. 2C-2 illustrates an embodiment wherein the light diverges from thecenter of the pixel group or the entire array, neither are a limitationof the invention, as in some applications, light from all pixels in agroup or the entire array may be directed in the same general direction,though normally in different angles to present the full image or imagesfor viewing in an undistorted form. This may require a counterdistortion at the directional modulator layer to achieve the undistortedimage for viewing. Further, the directional modulation layer may includetwo or more distinct pixel groups, one for presenting a first image atone location or depth, and one or more other images at one or moreadditional location or locations or depths.

In the foregoing description and in the claims, reference is made to adirectional modulation layer. It is to be understood that the word layeris used in a general sense to identify the layer or multiple layers thatdetermine the spatial modulation of the non-telecentric emissivemicro-pixel array light modulator. Also it should be understood thatwhile certain fabrication techniques for the directional modulationlayer have been described herein, each with respect to a respectiveembodiment, such techniques are also applicable to use in otherembodiments using the same form of directional modulation layer and/orfabrication sequence. Thus by way of example, the use of UV curablepolycarbonate polymer or the embossing to form a specific embodiment isexemplary, and such techniques and the sequence of operations forforming the resulting ROE are exemplary only, and the use of UV curablepolycarbonate polymer or embossing may be used to form any ROE baseddirectional modulation layer and to fabricate the non-telecentricemissive micro-pixel array light modulator of the present invention inany sequence of fabrication operations. Further, unless the contextdictates otherwise, references to a pixel group or pixel groups includesa reference to a group that encompasses the entire SSL imager emitterarea

Thus those skilled in the art will readily appreciate that variousmodifications and changes can be applied to the embodiments of theinvention without departing from its scope defined in and by theappended claims. It should be appreciated that the foregoing examples ofthe invention are illustrative only, and that the invention can beembodied in other specific forms without departing from the spirit oressential characteristics thereof. The disclosed embodiments, therefore,should not be considered to be restrictive in any sense. The scope ofthe invention is indicated by the appended claims, rather than thepreceding description, and all variations which fall within the meaningand range of equivalents thereof are intended to be embraced therein.

What is claimed is:
 1. An emissive directional light modulator comprising: a control layer; a solid state light (SSL) emitting display layer, comprising an array of light emitting pixels, positioned above and controllable from the control layer to emit light; and a directional modulation layer comprising pixel level refractive optical elements in the form of de-centered, or tilted, or spatially modulated, lenses comprising layers of dielectric materials with different indexes of refraction positioned above the SSL emitting display layer, each pixel level refractive optical element to directionally modulate light coupled to it from a corresponding light emitting pixel in a respective direction.
 2. The emissive directional light modulator of claim 1, wherein the solid state light emitting display layer comprising the array of light emitting pixels comprise a plurality of pixelated III/IV semiconductor layers to emit at least partially collimated, pixelated light.
 3. The emissive directional light modulator of claim 1, wherein each pixel level refractive optical element to directionally modulate light coupled to it from the corresponding light emitting pixel in a respective direction comprises each pixel level refractive optical element to directionally modulate light coupled to it from a corresponding light emitting pixel in a pre-selected respective direction.
 4. The emissive directional light modulator of claim 1, wherein the de-centered, or tilted, or spatially modulated, lenses comprising layers of dielectric materials with different indexes of refraction comprise de-centered, or tilted, or spatially modulated, micro-lenses comprising layers of dielectric materials with different indexes of refraction.
 5. The emissive directional light modulator of claim 1 wherein the array of light emitting pixels are divided into groups, each comprising a plurality of pixels.
 6. The emissive directional light modulator of claim 5 wherein each group of pixels is organized into a square, rectangle or hexagonal pattern.
 7. The emissive directional light modulator of claim 1 wherein the directional modulation layer comprises patterns, each directional modulation layer pattern corresponding to a respective pixel pattern, each directional modulation layer having the same directional modulation pattern.
 8. The emissive directional light modulator of claim 1 wherein the directional modulation layer comprises patterns, each directional modulation layer pattern corresponding to a respective pixel pattern, each directional modulation layer having a unique directional modulation pattern.
 9. The emissive directional light modulator of claim 5 wherein a group of light emitting pixels in the array of light emitting pixels in the solid state light (SSL) emitting display layer directionally modulates light coupled onto it to a respective converging pattern.
 10. The emissive directional light modulator of claim 5 wherein a group of light emitting pixels in the array of light emitting pixels in the solid state light (SSL) emitting display layer directionally modulates light coupled onto it to a respective diverging pattern.
 11. An emissive directional light modulator comprising: a control layer; a solid state light emitting display layer, comprising an array of light emitting pixels, positioned above and controllable from the control layer to emit light; and a directional modulation layer comprising pixel level diffractive optical elements in the form of a micro-grating comprising layers of metal rails or dielectric materials with different indexes of refraction positioned above the SSL emitting display layer, each pixel level diffractive optical element to directionally modulate light coupled to it from a corresponding light emitting pixel in a respective direction.
 12. The emissive directional light modulator of claim 11, wherein the pixel level diffractive optical elements in the form of a micro-grating comprise pixel level diffractive optical elements in the form of a transmission grating selected from one of a blazed grating or a rail grating.
 13. The emissive directional light modulator of claim 11, wherein the solid state light emitting display layer comprising the array of light emitting pixels comprise a plurality of pixelated III/IV semiconductor layers to emit at least partially collimated, pixelated light.
 14. The emissive directional light modulator of claim 11, wherein each pixel level diffractive optical element to directionally modulate light coupled to it from the corresponding light emitting pixel in a respective direction comprises each pixel level diffractive optical element to directionally modulate light coupled to it from a corresponding light emitting pixel in a pre-selected respective direction.
 15. An emissive pixel array light modulator comprising: a control layer; pixelated III/V semiconductor layers stacked above the control layer and controllable from the control layer to emit at least partially collimated, pixelated light; and a directional modulation layer comprising pixel level refractive optical elements in the form of de-centered, or tilted, or spatially modulated, lenses comprising layers of dielectric materials with different indexes of refraction positioned above the pixelated III/V semiconductor layers, each pixel level refractive optical element to directionally modulate light coupled onto it from a corresponding pixel to a respective direction relative to an axis perpendicular to the pixelated III/V semiconductor layers.
 16. The emissive pixel array light modulator of claim 15, wherein the pixelated III/V semiconductor layers to emit at least partially collimated, pixelated light that is modulated temporally. 